Method of making a fluid connection

ABSTRACT

Apparatus comprising a micro engineered structure and a capillary or other tube and a method for connecting the tube to the structure. The micro engineered structure is composed of at least one substrate  2  in which fluid flow channels  6  are formed, connecting to an aperture  12  into which the tube  14  is inserted. A sealant material is flowed into the aperture around the tube and then hardened in order to seal the tube within the aperture.

The present invention relates to fluid connections, in particular to afluid connection between an inlet capillary or other small bore tube anda microengineered fluidic structure. Hereinafter the term “small boretube” is taken to include capillary tubes and non-capillary tubes.

There is a growing interest in microengineered structures fortransporting microscopic amounts of fluid, wherein the fluid is subjectto chemical and/or biochemical processing and analysis. In particularour copending application WO96/12541 describes and claims method andapparatus for carrying out a diffusive transfer process between firstand second immiscible fluids, wherein first and second flow pathscommunicate with one another in a region which is such as to permit thefluids to form a stable open interface therein, and wherein the flowpaths in the interface region have a width normal to the interfacewithin the range 10 to 500 micrometers. As described, the apparatus istypically constructed by etching grooves in the surface of a siliconsheet, to form fluid flow channels, and to bond a cover layer of glassonto the silicon sheet. However the application does not address indetail the problem of making an external connection to themicroengineered device. It is desirable in this and many otherapplications of microfluidic devices, especially for analysis or wherefluids within the devices are to be monitored or controlled, thatconnections be formed to external tubing without formation of excessivedead spaces or stagnant areas. This can require connection of themicrofluidic device channels to capillary tubing of similar crosssectional dimensions.

Methods of making connections to capillary tubes are extremely welldocumented and are very diverse, depending on the specific application.For example, an end of the glass capillary may be surrounded by aplastic sheath for fixing securely in an inlet aperture of an apparatus,see for example EP-A-0698789 which describes a connection of capillarytubing to high pressure liquid chromatography apparatus. However, makinga force fit with a flexible sheath or other insert would not be suitablefor such a delicate microengineered structure as described in our abovecopending application. Further conventional connector structures forconnection to circular cross section capillary tubes by conventionalprocedures require structures with a recess of circular cross section,sometimes tapered, which are generally unavailable with microengineereddevices, and generally with dimensions greater than the thickness ofsubstrates conventionally used for construction of microengineeredstructures. For the purposes of the specification, microengineeredstructures is intended to mean structures formed with one or more thanone stacked substrates, each substrate being of generally planar formand of a thickness preferably 2 mm or less, and having fluid flowchannels formed therein, at least parts of such channels having across-sectional diameter less than 1000 micrometers. It will beunderstood that diameter is intended to mean the thickness or width fornon-circular cross sectional channels. It will further be appreciatedthat such channels may be extended in specific regions to form chambersetc. within the structure with dimensions greater than 1000 micrometers.The substrates are commonly formed from silicon, glass, ceramics,plastics or metal.

Connection of capillary tubes (commonly having dimensions between 50 and1000, desirably between 100 and 300 micrometers external diameter) tomicroengineered structures, especially those formed by bonding planaretched or formed substrates, generally requires low stress joiningtechniques. High temperature processes such as required to weld metals,ceramics, or glasses may generate damage such as substrate cracking ordelamination. Within relatively thin (generally <2 mm) substrates,especially in ceramics or glass, the formation and maintenance ofthreaded, interference, or compression joints is not well established.Sealing of joints usually therefore requires use of sealing material.

In Reston & Kolesar “Silicon-Micromachined Gas ChromatographySystem—Part 1”, Journal of Micromechanical Systems, IEEE/ASME, December1994, page 139 there is shown a method of connecting a gas inlet tube toa gas chromatograph comprising a spiral flow path, 300 μm wide and 10 μmdeep, etched into the surface of a silicon wafer substrate. A glassplate is bonded to the upper surface of the substrate over the spiralflow path, and a tapered gas feed through an aperture is formed in thelower surface of the silicon wafer communicating with the spiral flowpath. An end of a gas inlet tube, 254 μm in diameter, is inserted intothe tapered aperture, and an adhesive (epoxy resin) is applied aroundthe end of the inlet tube and the open part of the aperture in order toseal the tube within the aperture.

There are a number of problems and disadvantages associated with such anarrangement where the capillary tubes enters the device perpendicular tothe plane of substrates and the fluidic structures formed in thosesubstrates. One problem is that having a capillary tube connectionperpendicular to planar substrates and devices interferes with stackingof such substrates and devices to produce compact systems. Anotherproblem is that formation of vias through substrates for connection ofcapillary tubes perpendicular to substrates can excessively complicatedevice fabrication and reduce achievable device density and yields.Formation of vias through substrates with near parallel or slightlytapered bores matched to capillary tube dimensions can be difficult. Forstructures etched in glass or silicon the masking and etch timerequirements for the deep etching required for formation of such viascan be much more restrictive than those required for etching the fluidicchannel structures into the substrate surface.

Another problem with such an arrangement is that the length of capillarytube enclosed within the substrate is limited to the thickness of thesubstrate, and that the length of adhesive bond supported intimately bythe outer wall of the capillary tube and bore through the substrate issimilarly limited to the thickness of the substrate. This can result ina relatively weak and fragile seal. Application of further adhesivearound the capillary and onto the outer surface of the substrate mayimprove seal quality, but the improvement is often limited by poorbonding to planar substrate surfaces. Application of further adhesivearound the capillary and onto the outer surface of the substrate mayalso be undesirable due to the resultant increase in unit volume andinterference with packing together of units into a system. Similarly,bonding of conventional capillary connectors onto the substrate surfaceover a via may give poor seal quality, increase the area required forindividual devices, and interferes with device packing and stacking.

Another problem with such arrangements is that feeding adhesivematerials into the region between the capillary tube outer wall and thesides of the via bore sufficiently well to form a seal, but withoutadhesive entering and blocking or contaminating the fluidic channels andthe capillary tube itself, can be difficult. It is generally necessaryto use adhesive formulations of sufficiently high viscosity to preventrapid flow of adhesive by capillary action into the fluidic channels. Itis, however, generally difficult to observe or monitor and control howwell the adhesive has fed into the via regions desired.

A further problem with such arrangement is, particularly for gases, thatthe fluid must flow into the microengineered structure in a directionperpendicular to the direction of the fluid channels within thestructure and that the movement of the fluid through a right angle maycreate turbulence or other recirculating or mixin, processes and createflow conditions which are difficult to predict.

SUMMARY OF THE INVENTION

In a first aspect the present invention provides a method of connectinga capillary or other small bore tube to a microengineered structure toserve as a fluid flow port therefor, comprising: (1) providing amicroengineered structure having at least a first planar substrate withfluid flow channels formed therein, the or each substrate having firstand second opposite side surfaces extending substantially in the samedirection as the plane of the or each substrate and end surfacessubstantially normal to the plane of the or each substrate, and whereinan end surface of the at least one substrate has an aperture thereincommunicating with a said fluid flow channel; (2) providing a capillarytube or other small bore tube and inserting an end thereof into saidaperture in said end surface; and (3) flowing within the aperture aroundthe tube a sealant material, which is then hardened in order to seal thetube within the aperture.

The present invention provides in a further aspect ap apparatuscomprising a microengineered structure having a fluid coupling, thestructure comprising at least a first substrate with one or more fluidflow channels formed therein, the or each substrate being defined byfirst and second opposite side surfaces and end surfaces extending fromthe edges of the side surfaces, and including fluid inlet meanscomprising a capillary tube or other small bore tube inserted into anaperture formed in an end surface of the at least one substrate, whichcommunicates with a said fluid flow channel, and wherein a sealantmaterial is provided in the aperture, having been hardened in situaround the tube in the aperture subsequent to insertion of the tubing inthe aperture.

In a further aspect, the invention provides a microengineered structurefor a fluid coupling as set forth above wherein the structure comprisesat least a first substrate with one or more fluid flow channels formedtherein, the or each substrate being defined by first and secondopposite side surfaces and end surfaces extending from the edges of theside surfaces, an aperture being formed in an end surface of the atleast one substrate and communicating with a fluid flow channel andbeing dimensioned for receiving a capillary or other small bore tube.

The diameter of said aperture is sufficient to allow insertion of thetube (which may be 1000 micrometers diameter) together with sealantmaterial around the tube, and may be different to the fluid flow channeldiameter. Said aperture is such that the tube is positioned in the sameplane and preferably the same direction as a fluid flow path of thestructure, where the aperture is formed by a straight or gently curvedguide channel running from a fluid flow channel to a substrate endsurface.

As is common in microengineered structures, fluid flow channels may beformed in the surface of a first substrate, and a second substrate isstacked on the first substrate in order to seal the fluid flow channels.Alternatively the second substrate may have fluid flow channels formedin its lower surface which may communicate and co-operate with the flowchannels in the upper surface of the first substrate. As an alternativearrangement, the fluid flow channels may be formed within the bulk ofthe first substrate, and a second substrate is not necessary fordefining or sealing the fluid flow channels. In a further arrangement,the fluid flow channels and said aperture may be formed by buildingsuccessive layers on top of an initial substrate, the substrate withsuch layers then defining said first substrate, with a second substratepreferably sealing the top of the fluid flow channels.

Fluidic channels on microengineered structures, and guide channels fortube connections when formed on and between plane substrates will notgenerally be of circular cross section to match the connecting tubes.Etched, milled or sawn channels may generally have cross sections ofapproximately semicircular, triangular, trapezoid, or rectangular forms.Superposition of semicircular channels in first and second substratesmay yield approximately circular cross sections, but misalignment anddeviations from symmetry of a few micrometers at least are to beexpected. It is a requirement therefore that sealant for tubes connectedinto guide channels in the substrate plane must fill significant spacesaround the tubes.

In accordance with the invention a means is provided of establishing afluid flow connection to a microengineered structure, where the fluidmay flow directly into the structure in a direction parallel with thefluid flow channels within the structure. Thus there is no turbulence orother unpredictable flow conditions created. Further, since the seal iscreated subsequent to insertion of the tube by addition or formation ofa sealing material between the outer walls of the capillary tube and theinner wall of a channel section formed to contain the capillary tube,there is no excess pressures or thermal or other stresses created whichmight fracture the microengineering structure or cause a faulty seal.

An advantage of the invention is that the capillary tubes connect in theplane of the microengineered device allowing devices to be stacked. Afurther advantage is that the length of seal around the capillary tubewithin the device can be selected at the design stage without theconstraint of the substrate thickness and can be made sufficient toassure a good seal. A further advantage where one or more substrates istransparent is that the extent of the seal can be observed and radiationcuring low viscosity capillary filling sealant may be employed. Afurther advantage with some embodiments is that through vias do not needto be formed in the substrates. Where vias are proposed as describedbelow for sealant feeding, they may be remote from the microengineeredfluidic structures and need not be formed to the precision required forconnectors perpendicular to the substrate.

In addition to providing external fluid connections to microengineeredfluidic devices, a means is provided for linking fluid flow channels inseparate microfluidic devices which may be on separate substrates or mayshare one substrate or may be on a series of overlapping substratesbonded together.

The sealant material may comprise a substance, or mixture of substances,as will become clear below. The sealant material will be selected fromsubstances such as adhesives or cementing materials. These mostgenerally will be organic materials such as epoxy resins, but mayinclude other polymeric or polymerisable materials including inorganicmaterials or components.

In one preferred embodiment, the seal is formed by a method as describedand claimed in our European Patent Number EP-B-319175 (our Ref PA1314);the patent describes and claims a method of forming a solid article ofpredetermined shape from a liquid which can be cured by exposure toradiation, the method comprising the steps of providing a surface uponwhich the article is to be formed; exposing a predetermined region ofthe surface to a beam of radiation; supplying the liquid to an unexposedregion of the surface such that a solid barrier, defining a surface ofthe solid article, is created at the interface of the liquid and thebeam, and curing the liquid which has been supplied but not yet cured toform said solid article.

Thus to apply such a method to the present invention, a microengineeredstructure with fluidic channels in the substrate plane is fabricatedwith fluidic channels connecting as desired with straight or gentlycurved guide channels also in the substrate plane which run to asubstrate edge. The cross section of the guide channels is large enoughto allow tube insertion at the aperture formed at a substrate edge andfor the capillary tube to be fed into the structure to connect with thefluidic channels. A beam of, for example, ultra violet radiation isapplied through a transparent substrate material adjacent to the end ofa capillary tube positioned within an end aperture in a microengineeredstructure at the end limits of the desired position of the sealingsubstance. A radiation curing sealing substance is then fed into theopen end of the guide channel so that the liquid sealant flows aroundthe tube and into the aperture. The flow of liquid sealant may be drivenby hydrostatic or other applied pressure or by capillary forces or acombination of these forces. When it reaches the beam of radiation, itis hardened and cured. When a solid plug is created at the end, the beammay then be moved through the uncured substance so as to create acompletely hardened plug. Alternatively, the remainder of the substancemay be cured by broad exposure to UV or light, or by the application ofheat.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the accompanying drawings wherein:

FIG. 1 is a schematic plan view of a microengineered structure accordingto the invention with first and second fluid couplings providing inputand output ports;

FIG. 2 is a schematic side sectional view showing the method by which afirst fluid coupling of FIG. 1 is formed;

FIG. 3 is a schematic side sectional view showing the method by which asecond fluid coupling of FIG. 1 is formed;

FIGS. 4 and 5 are schematic side sectional views of the second fluidcoupling of FIG. 1 and a modification thereof;

FIGS. 6a-6 h are cross sectional views along the line 6—6 of FIG. 1 forvarious cross sections of fluid flow channels:

FIGS. 7 and 8 are schematic side sectional views of methods of formingrespective second and third embodiments of the invention;

FIGS. 9-12 are schematic side sectional views of methods of formingrespective fourth to seventh embodiments of the invention, and

FIGS. 13a-13 c are views illustrating a method in accordance with aneighth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 to 6, there is shown a microengineered structurecomprising a first silicon substrate 2 and a second glass substrate 4(FIG. 6) positioned face to face with the first substrate. The substrate2 is defined by upper and lower opposite side surfaces and end surfacesextending from the edges of the side surfaces. First substrate 2 has aserpentine fluid flow channel 6 formed in the upper surface thereofextending from an inlet port 8 to an outlet port 10, both formed in anend surface 11 of the substrate. It will be understood that the fluidflow channel may take various forms, depending upon the application, forexample, large area chambers etc. Fluid flow channel 6 has a diameter,width or thickness less than 1000 micrometers, typically 100micrometers, and may be of any suitable shape, for example triangularcross section.

Fluid inlet port 8 and fluid outlet port 10 are both formed withapertures 12 formed in end surface 11 and having the form of bores,having a width, as shown more than twice that of channel 6. Apertures 12receive capillary tubes 14 which may have a variety of sizes, forexample 300 micrometers external diameter, 200 micrometers internaldiameter, or 200 external, 150 internal, or 100 external 50 micrometersin diameter. The cross sectional shape of bores 12 may take a variety offorms as shown in FIG. 6 namely (a) triangular, (b) truncatedtriangular, (c) semi circular, (d) rectangular, and (e) circular. Itwill be noted that in FIG. 6 all of the bores 12 are formed in the uppersurface of substrate 2 apart from the circular bore of FIG. 6e which isformed partly in substrate 2 and partly in the lower surface ofsubstrate 4, but in general the bore could be formed in eithersubstrate. An alternative construction is shown in FIG. 6f and 6 gwherein a circular bore is formed wholly within substrate 2 by anetching technique involving cutting a vertical slit 19 in the uppersurface of substrate 2 and then generating a circular bore by an etchingtechnique. The slit will be sealed with sealant material 18 in thefinished form of the fluid coupling, as shown in FIG. 6g.

In FIG. 6h an alternative construction is shown wherein bore 12 andfluid flow channels 6 are formed on the upper surface of base substrate2 by building, by any suitable microengineering technique (defined byprinting, photolithography, lamination, and modified by etching ifrequired), layers 20 which define the side walls of the bore and fluidflow channels. The lower surface of the bore is defined by the uppersurface of base substrate 2 and the upper surface of the bore is definedby the lower surface of substrate 4 which is subsequently bonded tolayers 20. In such an arrangement, the upper surface of the layers 20define, in part, the upper surface of said first substrate.

For the sake of explaining the invention, the fluid coupling to inletport 8 is formed differently from that to outlet port 10. Referring toFIG. 2 which shows the method of forming the fluid coupling with inletport 8, capillary tube 14 is first inserted in to bore 12 close to apoint where bore 12 merges with flow channel 6 at a shoulder 16.Capillary tube 14 may be formed of silica, but may be glass, polymer oreven metal. A radiation curable material 18 is flowed into the open endof bore 12 and is such as to wick along bore 12 towards the end of tube14. A beam of ultra violet radiation 22 is directed at the end of tube14 from a light source 24 through transparent glass substrate 4 so thatwhen the liquid reaches the beam it is hardened. Once a solid plug hasbeen formed at the end of the tube 14, the light source may be movedalong the length of the tube so as to cure and harden the remainder ofliquid 18. Alternatively a second light source (not shown) is providedfor general exposure of the liquid 18.

In a variation of the method as shown in FIG. 3 which is adopted foroutlet port 10, a through aperture or via 30 is provided into which theradiation curable material is flowed. Otherwise the method is similar tothat shown in FIG. 2. The advantage of having a separate inlet via 30for the radiation curable material is where the material is notsufficiently fluid to permit it to be flown from the end of fluid inletport 8.

Referring to FIGS. 4 and 5, it is necessary when flowing material intothe fluid inlet port 8 to avoid injection of excess material, which mayflow into the fluid flow channel 6 and block the channel. Control isusually exercised by physical observation of the amount of materialinjected. In FIG. 4, a via 30 is positioned approximately mid waybetween the open end of the bore and fluid flow channel 6. When sealantmaterial starts emerging from the open end of the bore, as shown byswelling 40, an observer will know that the material has also reachedthe inner end of tube 14, and that further injection of material shouldbe stopped.

In FIG. 5 an alternative arrangement is shown for injecting a smalleramount of material, wherein a second via 50 is provided communicatingwith the bore and positioned adjacent to via 30. During inflow ofsealant material through via 30, an observer observes the ingress ofsealant material into via 50, as shown by swelling 52, and at that pointwill appreciate that a sufficient amount of sealant material has beeninserted and has reached the inner end of tube 14.

The radiation curing material may most generally be a UV or light curingpolymeric material. A variety of UV curing acrylic materials with arange of viscosities are available commercially (Norland UV Sealants,Norland Products Inc., New Brunswick, N.J. 08902, USA) and examples fromthat range ( e.g. high viscosity Norland 91, low viscosity Norland 81)or similar materials may be selected for use in the methods describedbelow where one or more of the substrate materials is transparent to theradiation.

Feeding sealant into the aperture at a substrate edge is particularlyconvenient for low viscosity sealant which feeds into the guide channelby capillary action. For such low viscosity sealant it is necessary toprovide a means of curing the sealant at the desired position in theguide channel by, for example, UV radiation so as to prevent the sealantrunning beyond the tube end and into the tube and the fluidic structure.For sufficiently viscous sealant, where flow is only significant underapplied pressure, curing may also be by radiation, but use ofnon-radiation curing sealant is also possible. Where a sufficientlyviscous sealant, especially a viscoelastic formulation, is employed suchthat flow within the guide channel is insignificant under capillaryaction but may be produced by pressure applied to the sealant at theaperture at a substrate edge, or by vacuum applied within themicroengineered structure, flow may be stopped by removing the pressuredifferential and the sealant cured or allowed to cure. An example ishigh viscosity two part epoxy which may be applied in e.g. Ciba GeigyAraldite 2005. The removal of the pressure differential may be inresponse to observation of the sealant front in the guide channel, or byobserving sealant extruding from the channel, possibly automated withthe aid of a vision system, or after a known time determined to producethe required amount of flow. The arrangements of FIGS. 4 and 5 would beparticularly suitable.

Where sufficient thermal control can be applied to parts of thestructure, a molten sealant material may be used which solidifies at thedesired position within the guide channel.

Referring to FIG. 7 and 8, these show a modification of the method ofFIG. 4 wherein an insert rod member 70 is inserted into tube 14 so as toproject beyond the end thereof into fluid flow channel 6. In FIG. 7,bore 12 and channel 6 are formed equally in substrate 2 and substrate 4,whereas in FIG. 8, bore 12 and channel 6 are formed wholly in substrate2. FIGS. 7 and 8 show a method for allowing sealant to go beyond end ofthe tube and reduce dead space. The insert 70, e.g. rod, fibre (possiblyoptical), wire, or narrower tube, is passed through tube 14 and intofluid channel 6. The sealant is allowed to flow beyond end of connectiontube 14 and around insert 70 before curing. The insert is removed bypulling out (e.g. for tungsten wire, or optical fibre, possibly coatedwith release agent), or melting (e.g. for polypropylene or PMMA fibre orrod, or Indium wire), or dissolving (e.g. for Cu or Ni tubes).

Referring now to the embodiment shown in FIG. 9, the substrates 2, 4 areof an opaque material. To permit the use of radiation ( e.g. UV) curingsealant, the radiation beam 90 is carried into the structure by anoptical fibre 92 which is passed inside tube 14 which is transparent.Alternatively, the fibre could be passed through the flow channels 6.Thus the coupling is formed as described above with reference to FIG. 2but with the fibre optic 92 inserted in the tube 14 and positioned sothat the region 94 at the end of the tube is bathed in radiation.Radiation curing sealant 18 flows up the guide channel towards the endof the tube and is cured by the radiation, thus preventing sealantpassing into tube and fluidic channels. After forming a plug in region94, the fibre optic is withdrawn slowly irradiating the rest of thesealant through the tube wall.

Referring now to FIG. 10, this shows a method for precipitant sealing byflowing two liquids into the system which react to form a solid. Thus,for example, concentrated viscous sodium silicate solution 100 is fed inthough via 102, while a much less viscous solution 104 of for example acalcium or magnesium salt (e.g. CaCl₂) is fed in through tube 14. Aninsoluble silicate precipitate is formed at region 108 at the end of thetube. By adjusting concentrations and flow rates it is ensured that theprecipitate remains in bore 12 around tube and progressively gets denseras Ca²⁺ ions diffuse into the silicate, while any precipitate formed inthe solution flowing through the centre of tube 14 gets swept away byforce of flow.

Referring to FIGS. 11 and 12, these are similar to FIGS. 7 and 8 exceptthat both substrates 2, 4 are opaque and it is therefore necessary touse a viscous, preferably viscoelastic material 110 which can beinjected into via 30 under pressure and which sets upon the release ofpressure and/or the application of heat.

In a further modification (not shown), of FIGS. 7 and 8, the capillarytube is dispensed with, and the sealing material is grown on the outsideof aperture 12 so as to boss onto which an external connection may bemade.

Referring now to FIGS. 13a to 13 c, these show an eighth embodiment ofthe invention wherein a tube 14 has a preformed sleeve insert 130 formedaround its inner end and of an external diameter less than that of bore12. This allows free insertion of tube 14 within the bore as shown inFIG. 13a. When fully positioned in the bore, heat is applied whichcauses the insert material to melt and form a seal between the tube 14and the inner walls of the bore 12 as shown in FIG. 13b.

In FIG. 13c, a sleeve insert material material 132 is provided whichexpands after insertion by application of a chemical reactant to changethe composition of the material, e.g. iron expanding to iron oxide. Uponthe removal of heat, the sealant material remains in the position shownin FIG. 13c.

It will be appreciated that in the embodiments of FIG. 13 and 10, inparticular, that where a plug is formed at the end of the tube, theremainder of the bore may subsequently be filled with a sealant materialinjected and hardened in accordance with any of the other embodiments,for example that in FIG. 2.

In addition, alternative sealants to radiation curable sealants may beemployed. For example, an anaerobic curing sealant which cures withinthe bore around the tube could be used, in which case sufficient controlon the sealant flow rate and/or cure time is needed, and also, possiblya flush device with nitrogen or other oxygen free gas. Alternatively thesealant material could be a viscous ceramic cement inserted by way of avia, as described with reference to FIG. 3. Example of such ceramiccements are Portland cement, plaster of Paris paste (hydrating gypsumCaSO₄), or phosphate cement (e.g., based on aluminium orthosposphatesolution and MgO.

What is claimed is:
 1. A method of providing a fluid connection betweena tube and a micro-engineered structure to serve as a fluid flow porttherefor, comprising: providing a micro-engineered structure having atleast one substrate with at least one fluid flow channel formed therein,said at least one substrate being defined by a first side surface and asecond side surface and a plurality of end surfaces extending from edgesof said first side surface and said second side surface, and at leastone of said plurality of end surfaces of said at least one substratehaving therein an aperture in communication with said at least one fluidflow channel; inserting a tube in said aperture of said at least one ofsaid plurality of end surfaces; and allowing a sealant material to flowwithin said aperture around said tube, said sealant material beingallowed to harden to provide a seal between said tube and said at leastone of said plurality of end surfaces within said aperture.
 2. Themethod of providing a fluid connection in accordance with claim 1,wherein: said tube is a capillary tube.
 3. The method of providing afluid connection in accordance with claim 1, further comprising:directing a beam of radiation at an inner end of said tube within saidaperture; wherein said sealant material comprises a radiation curablematerial, said sealant material being hardened upon exposure to saidbeam of radiation as said sealant material is introduced into saidaperture.
 4. The method of providing a fluid connection in accordancewith claim 3, further comprising: moving said beam of radiation alongsaid tube to harden said sealant material within said aperture once asolid plug is formed at said inner end of said tube.
 5. The method ofproviding a fluid connection in accordance with claim 4, wherein: saidat least one substrate is made of a transparent material; and saiddirecting said beam of radiation step includes directing said beam ofradiation at said sealant material through said at least one substrate.6. The method of providing a fluid connection in accordance with claim4, wherein: said tube is made of a transparent material; and saiddirecting said beam of radiation step includes directing said beam ofradiation at said sealant material through said tube.
 7. The method ofproviding a fluid connection in accordance with claim 1, wherein: saidsealant material is viscous, and allowed to flow into said apertureunder pressure, said sealant material being hardened upon subsequentremoval of said pressure.
 8. The method of providing a fluid connectionin accordance with claim 7, wherein: said sealant material isviscoelastic.
 9. The method of providing a fluid connection inaccordance with claim 1, wherein: said sealant material is inserted intosaid tube in a molten form, and hardened by subsequent cooling of saidsealant material.
 10. The method of providing a fluid connection inaccordance with claim 1, wherein: said sealant material is a cementinserted into said aperture in a fluid form, and subsequently hardened.11. The method of providing a fluid connection in accordance with claim1, wherein: said sealant material comprises at least a first substanceintroduced in said aperture and a second substance introduced throughsaid tube, said first and said second substances mixing and reactingtogether at an inner end of said tube to create a seal within saidaperture around said tube.
 12. The method of providing a fluidconnection in accordance with claim 1, further comprising: forming acylindrical insert on an end of said tube, an external dimension of saidcylindrical insert permitting free insertion of said tube in saidaperture; and melting said cylindrical insert when said tube is insertedin said aperture to seal said tube to an inner surface of said at leastone of said end surfaces within said aperture.
 13. The method ofproviding a fluid connection in accordance with claim 1, furthercomprising: forming a via in said at least one substrate, said viapermitting said sealant material to flow therethrough to said aperture.14. The method of providing a fluid connection in accordance with claim1, wherein: an amount of said sealant material allowed to flow into saidaperture is determined by physical observation of said sealant materialwithin said aperture.
 15. The method of providing a fluid connection inaccordance with claim 13, further comprising: providing a further via insaid at least one substrate to permit observation of said sealantmaterial flowing along said aperture and into said further via, saidobservation allowing a determination whether sufficient material hasflowed into said aperture.
 16. The method of providing a fluidconnection in accordance with claim 1, further comprising: inserting arod member through said tube into said at least one fluid flow channelin order to permit said sealant material to flow into said aperture asclose as possible to said at least one fluid flow channel withoutblocking said at least one fluid flow channel; and withdrawing said rodmember from said tube subsequent to hardening of said sealant material.17. The method of providing a fluid connection in accordance with claim1, further comprising: forming said aperture with a straight guidechannel running from said at least one fluid flow channel to said atleast one of said plurality of end surfaces.
 18. The method of providinga fluid connection in accordance with claim 1, further comprising:forming said aperture with a curved guide channel running from said atleast one fluid flow channel to said at least one of said plurality ofend surfaces.
 19. The method of providing a fluid connection inaccordance with claim 1, further comprising: forming said aperture witha bore running from said at least one fluid flow channel to said atleast one of said plurality of end surfaces.
 20. A method of providing afluid flow port on a micro-engineered structure for allowing externalfluid connection thereto, comprising: providing a micro-engineeredstructure having at least one substrate with at least one fluid flowchannel formed therein, said at least one substrate being defined by afirst side surface and a second side surface and a plurality of endsurfaces extending from edges of said first side surface and said secondside surface, and at least one of said plurality of end surfaces of saidat least one substrate having therein an aperture in communication withsaid at least one fluid flow channel; growing a sealant material on anoutside of said aperture to provide a structure, said structure allowingan external fluid connection thereto.